A Vector<FlexItem> can probably be referred to as simply just FlexItems
<rdar://problem/113777139>
Pull request: https://github.com/WebKit/WebKit/pull/16629
Committed 266864@main (d8aa063fb4e4): <https://commits.webkit.org/266864@main> Reviewed commits have been landed. Closing PR #16629 and removing active labels.